Quantitative analysis of biodegradable amphipmlic poly(L-lactide)-block-poly(ethyleneglycol)-block-poly(L-lactide) by using TG, FTIR and NMR

The thermogravimetric analysis (TG) of two series of tri-block copolymers based on poly(L,L-lactide) (PLLA) and poly(ethyleneglycol) (PEG) segments, having molar mass of 4000 or 600 g mol(-1), respectively, is reported. The prepared block copolymers presented wide range of molecular masses (800 to 47500 g mol(-1)) and compositions (16 to 80 mass% PEG). The thermal stability increased with the PLLA and/or PEG segment size and the tri-block copolymers prepared from PEG 4000 started to decompose at higher temperatures compared to those copolymers from PEG 600. The copolymers compositions were determined by thermogravimetric analysis and the results were compared to other traditional quantitative spectroscopic methods, hydrogen nuclear magnetic resonance spectrometry ((HNMR)-H-1) and Fourier transform infrared spectrometry (FTIR). The PEG 4000 copolymer compositions calculated by TG and by (HNMR)-H-1, presented differences of 1%, demonstrating feasibility of using thermogravimetric analysis for quantitative purposes.